Anti-vibration rubber

ABSTRACT

An anti-vibration rubber of the present invention is an anti-vibration rubber for washing machines. In temperature variance measurement of dynamic viscoelasticity at a frequency of 30 Hz, the anti-vibration rubber has a maximum loss factor at a temperature of −10° C. to 40° C., both inclusive, and has a loss factor of 0.4 or more in the entire temperature range of −10° C. to 40° C., both inclusive, at the frequency of 30 Hz.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a Continuation application of U.S. patentapplication Ser. No. 15/525,889, filed on May 10, 2017, which claimspriority from PCT Application Serial No. PCT/JP2016/063336, filed onApr. 28, 2016, which claims priority from Japanese Patent ApplicationSerial No. 2015-092808, filed on Apr. 30, 2015, the contents of whichare hereby incorporated herein in their entirety by this reference.

TECHNICAL FIELD

The present invention relates to anti-vibration rubbers, and moreparticularly to anti-vibration rubbers for washing machines.

BACKGROUND ART

Washing machines have leg rubbers, which are made of an elastic body, atthe four corners of their bottom surfaces for reduced vibration andimproved ease of installation. Examples of such washing machines includedrum-type washing machines described in Japanese Unexamined PatentApplication Publication Nos. 2006-204715 (Patent Literature 1) andH11-164986 (Patent Literature 2).

As shown in FIG. 1, a drum-type washing machine 1 disclosed in PatentLiterature 1 includes: an outer cabinet 4 that has a base 3 at thebottom; a wash tub 6 that is accommodated in the outer cabinet 4 and iselastically supported on its lower side by anti-vibration means; and aspin tub 8 (drum) that is accommodated in the wash tub 6 and is drivento turn by drive means. The spin tub 8 functions as a common tub forwash, rinse, spin, and dry cycles. The drum-type washing machine ofPatent Literature 1 has elastic leg rubbers 31 attached to the fourcorners of the base 3.

As shown in FIG. 2, a drum-type washing machine 2 of Patent Literature 2uses a structure in which a wash tub 6 accommodating a spin tub 8 issuspended from an outer cabinet 4 by spring bodies 11. The drum-typewashing machine 2 further has an anti-vibration damper 12 in order toreduce vibration when a dry cycle is started. The drum-type washingmachine of Patent Literature 2 also has leg rubbers 31 under fixed legsfixed to the bottom of the outer cabinet 4.

CITATION LIST Patent Literatures

Patent Literature 1: Japanese Unexamined Patent Application PublicationNo. 2006-204715

Patent Literature 2: Japanese Unexamined Patent Application PublicationNo. H11-164986

SUMMARY OF INVENTION Technical Problem

The drum-type washing machine disclosed in Patent Literature 1 has astructure that is effective when expected installation locations are inbuildings with low stiffness such as Japanese-style houses with woodenstructures and when vibration and noise are desired to be reduced. Thedrum-type washing machine disclosed in Patent Literature 2 has a morestandard structure than Patent Literature 1, and this structure iscommon in the world market.

In both of the structures of Patent Literatures 1 and 2, the drum-typewashing machine operates with action and spin speed corresponding toeach cycle (wash, rinse, spin, and dry). The spin speed of the drum needbe increased for the spin cycle because as large a centrifugal force aspossible is required to squeeze out as much water as possible.Accordingly, recent washing machines are used in the region from thestart of the dry cycle (spin speed: 0 rpm) to their maximum spin speed(e.g., 1,800 rpm), and the washing machines always go through anintermediate region thereof when they are started and stopped. Thewashing machines are therefore temporarily used in this intermediateregion. In this case, the body (outer cabinet) of the washing machinemay resonate with the spin speed of the drum in a region where the spinspeed of the drum matches the natural frequency of the body of thewashing machine, which amplifies vibration.

In Patent Literature 1, elastic auxiliary legs are further attachedbetween the leg rubbers in the four corners in order to restrainvibration and noise. In Patent Literature 2, the leg rubbers formed bycombination of a low hardness, low resilience rubber member and a highhardness rubber member are used in order to prevent an increase invibration in the spin cycle. However, vibration is not sufficientlyreduced by the techniques disclosed in Patent Literatures 1 and 2.

In view of the above problems, it is an object of the present inventionto provide an anti-vibration rubber that reduces vibration.

Solution to Problem

The inventors looked at the fact that anti-vibration rubbers for washingmachines are used in the temperature range of −10° C. to 40° C., bothinclusive, and conceived that vibration can be reduced by increasing aloss factor, which is an index of vibration energy absorption, in thistemperature range. The inventors arrived at the idea that, for washingmachines with a natural frequency in a high frequency region close totheir maximum spin speed, vibration can be reduced by implementing ananti-vibration rubber having a high loss factor in the high frequencyregion, and thus completed the invention.

An anti-vibration rubber of the present invention is an anti-vibrationrubber for washing machines. In temperature variance measurement ofdynamic viscoelasticity at a frequency of 30 Hz, the anti-vibrationrubber has a maximum loss factor at a temperature of −10° C. to 40° C.,both inclusive, and has a loss factor of 0.4 or more in an entiretemperature range of −10° C. to 40° C., both inclusive, at the frequencyof 30 Hz.

Since the anti-vibration rubber of the present invention has a maximumloss factor within the temperature range of −10° C. to 40° C., bothinclusive, a high loss factor can be maintained in the temperature rangein which the anti-vibration rubber for washing machines is used. Sincethe anti-vibration rubber has a loss factor of 0.4 or more in the entiretemperature range of −10° C. to 40° C., both inclusive, at the frequencyof 30 Hz, a high loss factor can always be maintained in a high spinspeed region close to a maximum spin speed of washing machines in thetemperature range in which washing machines are used. Vibration cantherefore be reduced.

Preferably, the anti-vibration rubber of the present invention containsa polymer component, and the polymer component mainly contains butylrubber. An anti-vibration rubber having a high loss factor in thetemperature range of −10° C. to 40° C., both inclusive, can thus beimplemented.

In the anti-vibration rubber of the present invention, it is morepreferable that the butyl rubber be halogenated butyl rubber. This canreduce compression set.

It is preferable that the anti-vibration rubber of the present inventionfurther contain a metal oxide as a vulcanizing agent. This can reducecompression set.

It is preferable that the anti-vibration rubber of the present inventionfurther contain a tackifying resin. An anti-vibration rubber having ahigh loss factor in the temperature range of −10° C. to 40° C., bothinclusive, can thus be implemented.

It is preferable that the anti-vibration rubber of the present inventionfurther contain a processing aid. An anti-vibration rubber with improvedprocessability can thus be implemented.

Advantageous Effects of Invention

As described above, the anti-vibration rubber of the present inventioncan reduce vibration.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cutaway side view schematically showing a washing machinewith anti-vibration rubber which is disclosed in Patent Literature 1.

FIG. 2 is a sectional view schematically showing a washing machine withanti-vibration rubber which is disclosed in Patent Literature 2.

FIG. 3 is a graph showing loss factors of anti-vibration rubbers ofSamples 1 to 6.

FIG. 4 is a graph showing loss factors of anti-vibration rubbers ofSamples 7 to 10.

FIG. 5 is a graph showing the amounts of amplitude measured with theanti-vibration rubbers of Samples 1 to 9 being attached to washingmachines.

DESCRIPTION OF EMBODIMENTS

An embodiment of the present invention will be described below. In thefigures described below, the same or corresponding portions are denotedwith the same reference characters, and description thereof will not berepeated.

An anti-vibration rubber of an embodiment of the present invention is ananti-vibration rubber for washing machines. Specifically, as shown inFIGS. 1 and 2, the anti-vibration rubber of the present embodiment isused for leg rubbers 31 of washing machines and is disposed at positionssimilar to those of the leg rubbers 31 of FIGS. 1 and 2. Theanti-vibration rubber of the present embodiment is suitably used forwashing machines with a natural frequency at 1,000 rpm or higher. Thatis, the anti-vibration rubber of the present embodiment is suitably usedfor washing machines including a wash tub holding therein a spin tubthat turns, and an outer cabinet accommodating the wash tub and having anatural frequency at 1,000 rpm or higher.

In temperature variance measurement of dynamic viscoelasticity at afrequency of 30 Hz, the anti-vibration rubber of the present embodimenthas a maximum loss factor at a temperature of −10° C. to 40° C., bothinclusive, preferably 0° C. to 40° C., both inclusive, and morepreferably 5° C. to 35° C., both inclusive.

The anti-vibration rubber has a loss factor of 0.4 or more, preferably0.45 or more, in the entire temperature range of −10° C. to 40° C., bothinclusive, at a frequency of 30 Hz. The anti-vibration rubber preferablyhas a loss factor of 0.5 or more, more preferably 0.6 or more, in theentire temperature range of 0° C. to 40° C., both inclusive, at thefrequency of 30 Hz. In view of anti-vibration properties, the higher theloss factor is, the more preferable.

The “loss factor (tan δ)” is one of evaluation indices of anti-vibrationproperties of anti-vibration materials, and for example, is a value thatis measured according to JIS K 6394 (testing methods and small testingdevices for dynamic properties of vulcanized rubber and thermoplasticrubber). A high loss factor indicates that the anti-vibration rubber hasa strong ability to reduce vibration.

Compression permanent set of the anti-vibration rubber is preferably 30%or less. The “compression permanent set” is a value that is measuredaccording to JIS K 6262 (methods for determining compression set ofvulcanized rubber and thermoplastic rubber at ambient, high, and lowtemperatures). Low compression permanent set indicates that theanti-vibration rubber has a strong ability to recover when compressedfor a long period of time.

Such an anti-vibration rubber (vulcanized anti-vibration rubber) of thepresent embodiment is made of a rubber composition containing a polymercomponent, a tackifying resin, a processing aid, a vulcanizing agent, avulcanization accelerator, and a filler. The rubber composition will bedescribed below.

The polymer component is not particularly limited as long as it is arubber material. However, it is preferable that the polymer componentmainly contain butyl rubber. As used herein, “mainly contain” means 50mass % or more of the total polymer component.

Examples of the butyl rubber include halogenated butyl rubber andregular butyl rubber, and halogenated butyl rubber is preferred.Examples of the halogenated butyl rubber include chlorobutyl rubber andbrominated butyl rubber, and chlorobutyl rubber is preferred. Either asingle kind of polymer component or a mixture of two or more kinds ofpolymer components may be used, but it is preferable to use a singlekind of halogenated rubber. That is, it is preferable that the polymercomponent mainly contain halogenated butyl rubber and the remainder ofthe polymer component be unavoidable impurities.

The tackifying resin to be used herein has a melting point in the rangeof 90° C. to 150° C., both inclusive. Examples of the tackifying resininclude rosin resin, terpene resin, petroleum resin, coal resin,phenolic resin, xylene resin, and coumarone resin. One of these resinsmay be used solely or a mixture of two or more of these resins may beused. It is preferable that the tackifying resin be one or more kinds ofresins selected from the group consisting of rosin resin, terpene resin,petroleum resin, coal resin, phenolic resin, and xylene resin.

The tackifying resin preferably has a melting point of 90° C. or higher,more preferably 100° C. or higher, even more preferably 120° C. orhigher, most preferably in the range of 120° C. to 150° C., bothinclusive.

The content of the tackifying resin is preferably in the range of 10 to60 parts by mass, both inclusive, more preferably 25 to 60 parts bymass, both inclusive, even more preferably 35 to 60 parts by mass, bothinclusive, most preferably 40 to 60 parts by mass, both inclusive, per100 parts by mass of the polymer component. In particular, the contentof the tackifying resin having a melting point of 120° C. to 150° C.,both inclusive, is preferably in the range of 40 to 60 parts by mass,both inclusive, per 100 parts by mass of the polymer component.

The vulcanizing agent is not particularly limited. Examples of thevulcanizing agent include sulfur, a sulfur-based vulcanizing agent suchas tetraalkylthiuram disulfide, a metal oxide, an organic peroxide, anda resin vulcanizing agent. One of these vulcanizing agents may be usedsolely or a mixture of two or more of these vulcanizing agents may beused. It is preferable that the vulcanizing agent contain a metal oxide.The metal oxide is not particularly limited. Examples of the metal oxideinclude zinc oxide and magnesium oxide, and zinc oxide is preferred.

The content of the vulcanizing agent is preferably in the range of 1 to50 parts by mass, both inclusive, more preferably 3 to 10 parts by mass,both inclusive, per 100 parts by mass of the polymer component.

The vulcanization accelerator is not particularly limited. Examples ofthe vulcanization accelerator include thiazoles such as dibenzothiazyldisulfide, sulfenamides such as N-cyclohexyl-2-benzothiazolesulfenamide, thiurams such as tetramethylthiuram disulfide, anddithiocarbamates such as zinc dimethyldithiocarbamate. One of thesevulcanization accelerators may be used solely or a mixture of two ormore of these vulcanization accelerators may be used. The content of thevulcanization accelerator is preferably in the range of 0.5 to 5 partsby mass, both inclusive, per 100 parts by mass of the polymer component.

The vulcanizing agent means a compounding agent that preferentiallyreacts with a rubber material. The vulcanization accelerator(vulcanization accelerator aid) means a compounding agent thatfacilitates a reaction that is caused by the vulcanizing agent andaccelerates the reaction or that increases crosslink density.

The processing aid is not particularly limited as long as it is amaterial that improves processability. Examples of the processing aidinclude stearic acid and amines. One of these processing aids may beused solely or a mixture of two or more of these processing aids may beused. The processing aid is preferably a compound having a fatty acidskeleton, more preferably stearic acid. The content of the processingaid is preferably in the range of 0.3 to 10 parts by mass, bothinclusive, more preferably 0.3 to 5 parts by mass, both inclusive, per100 parts by mass of the polymer component. If the content of theprocessing aid is less than 0.3 parts by mass, processability duringkneading is not sufficiently improved. If the content of the processingaid is more than 10 parts by mass, compression set may be deteriorated.

The filler is not particularly limited. Examples of the filler includecarbon black, silica, calcium carbonate, talc, clay, and titanium white.One of these fillers may be used solely or a mixture of two or more ofthese fillers may be used.

The rubber composition may further contain a softener, a plasticizer, ananti-aging agent, a reinforcing agent, etc. as appropriate in additionto the substances described above.

A method for producing the anti-vibration rubber of the presentembodiment will be described below. First, a polymer component, atackifying resin, a vulcanizing agent, a vulcanization accelerator, anda filler are kneaded with an open roll, an internal kneading machine(e.g., Intermix, kneader, or Banbury mixer), etc. to produce anunvulcanized rubber composition. Next, the rubber compression isvulcanized by, e.g., compression press molding, preferably by transfermolding etc. The anti-vibration rubber of the present embodiment canthus be produced.

EXAMPLES

The present invention will be described in more detail below based onexamples. However, the present invention is not limited to the followingexamples.

Example 1

Table 1 shows the contents of each component and the evaluation resultsof Samples 1 to 10. Table 2 specifically shows the components listed inTable 1.

(Samples 1 to 6)

A polymer component, a tackifying resin, a filler, a vulcanizing agent,a vulcanization accelerator, and a processing aid were kneaded with akneading machine as shown in Tables 1 and 2 to produce rubbercompositions of Samples 1 to 6. Each of the rubber compositions ofSamples 1 to 6 was then vulcanized by heating at 160° C. for 30 minutesto produce anti-vibration rubbers of Samples 1 to 6. The anti-vibrationrubbers of Samples 1 to 6 contain halogenated butyl rubber as a polymercomponent, a tackifying resin, a filler, a processing aid, a vulcanizingagent, and a vulcanization accelerator, and the remainder is unavoidableimpurities.

(Samples 7 to 9)

A polymer component, a filler, a vulcanizing agent, a vulcanizationaccelerator, a processing aid, and a softener were kneaded with akneading machine as shown in Tables 1 and 2 to produce rubbercompositions of Samples 7 to 9. Each of the rubber compositions ofSamples 7 to 9 was then vulcanized by heating at 160° C. for 30 minuteswith a molding machine to produce anti-vibration rubbers of Samples 7 to9.

(Sample 10)

A polymer component, a tackifying resin, a filler, a vulcanizing agent,a vulcanization accelerator, and a processing aid were kneaded with akneading machine as shown in Tables 1 and 2 to produce a rubbercomposition of Sample 10. The rubber composition of Sample 10 was thenvulcanized by heating at 160° C. for 30 minutes to produce ananti-vibration rubber of Sample 10.

(Loss Factor)

Loss factors of the anti-vibration rubbers of Samples 1 to 10 weremeasured according to JIS K 6394 with a dynamic viscoelasticitymeasuring device Rheogel-E4000 made by UBM. The measurement was carriedout under the following conditions. Test pieces of 15 mm long, 5 mmwide, and 2 mm thick were used and were strained in the verticaldirection at a test interval (interval between upper and lower chucks)of 10 mm, initial strain (mean strain) of 10% (1 mm), amplitude of±0.02% (±2 μm), and a frequency of 30 Hz. The results are shown in Table1 and FIGS. 3 and 4.

(Evaluation Method)

Anti-vibration properties, processability, and compression permanent setwere measured for the anti-vibration rubbers of Samples 1 to 10.

For anti-vibration properties, the anti-vibration rubbers of Samples 1to 10 were used as leg rubbers of washing machines with a naturalfrequency at 1,400 rpm, and vibration amplitude (amount of amplitude) at25° C. was measured. The results are shown in FIG. 5 and Tables 1 and 3.Regarding “Anti-Vibration Properties” in Table 1, “X” indicates that theamount of amplitude at the natural frequency of the washing machine was0.2 mm or less, “Y” indicates that the amount of amplitude at thenatural frequency of the washing machine was more than 0.2 mm and 0.3 mmor less, and “Z” indicates that the amount of amplitude at the naturalfrequency of the washing machine was more than 0.3 mm. In Table 3,“Ratio” indicates the value of the amount of amplitude of each samplerelative to the amount of amplitude of the anti-vibration rubbers ofSamples 7 and 8 at the natural frequency of the washing machine being1.00, and “Rate of Decrease” indicates the rate (%) of decrease inamount of amplitude relative to the amount of amplitude of theanti-vibration rubbers of Samples 7 and 8 at the natural frequency ofthe washing machines being 100%.

Processability was determined based on whether the unvulcanized rubberadhered to the kneading machine in the kneading process or not. Theresults are shown in Table 1. In Table 1, “X” indicates that there wasno adhesion of the unvulcanized rubber and thus indicates satisfactoryprocessability.

Compression set (c-set) was measured according to JIS K 6262 afterstorage at a temperature of 100° C. and a compression rate of 25% for 24hours. The results are shown in Table 1.

TABLE 1 Sample Sample Sample 1 Sample 2 Sample 3 Sample 4 Sample 5Sample 6 Sample 7 Sample 8 9 10 Polymer A 100 100 100 100 100 100 100Component B 100 C 100 D 100 Tackifying Resin A 40 B 60 C 55 D 55 E 25 F10 G 20 Filler A 55 60 60 60 65 55 60 40 20 40 B 20 C 40 Softener A 2015 B 10 Processing Aid A 0.3 1 1 3 1 1 1 1 1 1 B 2 Vulcanizing A 5 5 5 55 5 5 5 Agent B 2 2 C D Vulcanization A 5 5 Accelerator B 1 1 1 1 1 1 1Vulcanization C 1 Accelerator Aid D 4 Peak tan δ 25 35 32 30 5 −10 −40or −25 −25 20 Temperature (° C.) lower tan δ (25° C./10 Hz) 1.31 1.201.25 1.24 0.93 0.66 0.16 0.14 0.38 1.21 Anti-Vibration X X X X Y Y Z Z ZZ Properties Processability X X X X X X X X X X Compression Set (%) 1617 16 25 11 10 18 14 9 70

TABLE 2 Compound Trade Name Company Name Polymer A Chlorobutyl RubberChlorobutyl 1066 JSR Corporation Component B EPDM EP-33 JSR CorporationC CR SKYPRENE B-5A Tosoh Corporation D NBR N215 JSR CorporationTackifying A Hydrogenated Terpene Resin CLEARON P150 YASUHARA CHEMICALCO., LTD. Resin B Hydrogenated Petroleum Resin I-MARV P-125 IdemitsuKosan Co., Ltd. C Alicyclic Saturated Hydrocarbon Resin ARKON P-120ARAKAWA CHEMICAL INDUSTRIES, LTD. D Aromatic Modified Terpene Resin YSRESIN TO125 YASUHARA CHEMICAL CO., LTD. E Aromatic Modified TerpeneResin YS RESIN TO105 YASUHARA CHEMICAL CO., LTD. F Alicyclic SaturatedHydrocarbon Resin ARKON P-100 ARAKAWA CHEMICAL INDUSTRIES, LTD. GCoumarone Resin G-90 NITTO CHEMICAL CO., LTD. Filler A Carbon Black N774GAZPROM B MT carbon Thermax N990 Cancarb Limited C Calcium CarbonateSilver-W SHIRAISHI CALCIUM KAISHA, LTD. Softener A Paraffinic ProcessOil SUMPAR 110 JAPAN SUN OIL COMPANY, LTD. B Naphthenic Process OilNCL-22 TANIGUCHI SEKIYU KK Processing A Stearic Acid LUNAC S-70 KaoCorporation Aid B Mixture of Metal Salt of Fatty Acid and Exton L-7Kawaguchi Chemical Industry Co., LTD. Ester Vulcanizing A Zinc OxideZinc Oxide THE HONJO CHEMICAL CORPORATION Agent B DicumylperoxidePERCUMYL D NOF CORPORATION C Sulfur SULFAX A Tsurumi Chemical IndustryCo., ltd. D Alkylphenol Formaldehyde Resin TACKIROL 201 Taoka ChemicalCo., Ltd. Vulcanization A Zinc Oxide Zinc Oxide THE HONJO CHEMICALCORPORATION Accelerator B ZnEDC NOCCELER Ez OUCHI SHINKO CHEMICALINDUSTRIAL CO., LTD. Vulcanization C ETU SANCELLER 22C SANSHIN CHEMICALINDUSTRY CO., LTD. Accelerator D Magnesium Oxide Magnesium Oxide KyowaChemical Industry Co., Ltd. Aid 1000-1

TABLE 3 Amount of Amplitude Rate of (mm) Ratio Decrease (%) sample 1~40.195 0.39 61.0 sample 5 0.250 0.50 50.0 sample 6 0.300 0.60 40.0 sample7.8 0.500 1.00 — sample 9 0.375 0.75 25.0

(Evaluation Results)

As shown in FIG. 3 and Table 1, in temperature variance measurement ofdynamic viscoelasticity at a frequency of 30 Hz, each of theanti-vibration rubbers of Samples 1 to 6 had a maximum loss factor at atemperature of −10° C. to 40° C., both inclusive, and had a loss factorof 0.4 or more in the entire temperature range of −10° C. to 40° C.,both inclusive, at the frequency of 30 Hz. In particular, as shown inFIG. 3 and Table 1, in temperature variance measurement of dynamicviscoelasticity at a frequency of 30 Hz, each of the anti-vibrationrubbers of Samples 1 to 5 had a maximum loss factor at a temperature of0° C. to 40° C., both inclusive, and had a loss factor of 0.5 or more inthe entire temperature range of 0° C. to 40° C., both inclusive, at thefrequency of 30 Hz.

As shown in FIG. 4 and Table 1, in temperature variance measurement ofdynamic viscoelasticity at a frequency of 30 Hz, each of theanti-vibration rubbers of Samples 7 to 9 had a maximum loss factor at atemperature of −25° C. or lower, and each of the anti-vibration rubbersof Samples 7 to 10 had a loss factor of less than 0.4 in a part of thetemperature range of −10° C. to 40° C., both inclusive, at the frequencyof 30 Hz.

As shown in FIG. 5 and Table 3, regarding the anti-vibration rubbers ofSamples 1 to 6, each having a maximum loss factor at a temperature of−10° C. to 40° C., both inclusive, and having a loss factor of 0.4 ormore in the entire temperature range of −10° C. to 40° C., bothinclusive, at the frequency of 30 Hz, their amounts of amplitude at thenatural frequency of the washing machine were able to be reduced ascompared to Samples 7 to 10. It is therefore found that theanti-vibration rubbers of Samples 1 to 6 achieve low vibration. Inparticular, regarding the anti-vibration rubbers of Samples 1 to 5, eachhaving a maximum loss factor at a temperature of 0° C. to 40° C., bothinclusive, and having a loss factor of 0.5 or more in the entiretemperature range of 0° C. to 40° C., both inclusive, at the frequencyof 30 Hz, their amounts of amplitude at the natural frequency of 1,000rpm or higher were able to be reduced significantly. Regarding theanti-vibration rubbers of Samples 1 to 4, each having a maximum lossfactor at a temperature of 20° C. to 40° C., both inclusive, and havinga loss factor of 0.8 or more in the entire temperature range of 20° C.to 40° C., both inclusive, at the frequency of 30 Hz, their amounts ofamplitude at the natural frequency of 1,000 rpm or higher were able tobe reduced more significantly. The amounts of amplitude of theanti-vibration rubbers of Samples 1 to 6 were small as shown in FIG. 5and Table 3. It is therefore found that the anti-vibration rubbers ofSamples 1 to 6 can reduce noise.

Although not shown in FIG. 5, the anti-vibration rubber of Sample 10 hasa high loss factor at around 20° C. at the frequency of 30 Hz, but ahigh loss factor cannot be maintained in the low temperature range of−10° to 5° C. It was thus confirmed the anti-vibration rubber of Sample10 had poor anti-vibration properties.

According to Example 1, it was confirmed that anti-vibration rubbershaving a maximum loss factor at a temperature of −10° C. to 40° C., bothinclusive, and having a loss factor of 0.4 or more in the entiretemperature range of −10° C. to 40° C., both inclusive, at the frequencyof 30 Hz in temperature variance measurement of dynamic viscoelasticityat the frequency of 30 Hz can reduce vibration when attached to washingmachines. In particular, it was confirmed that the anti-vibration rubberof the present invention is suitably used for washing machines with anatural frequency at 1,000 rpm or higher.

It was also confirmed that anti-vibration rubbers having a maximum lossfactor at a temperature of −10° C. to 40° C., both inclusive, and havinga loss factor of 0.4 or more in the entire temperature range of −10° C.to 40° C., both inclusive, at the frequency of 30 Hz in temperaturevariance measurement of dynamic viscoelasticity at the frequency of 30Hz can be implemented by using a rubber composition containing a polymercomponent mainly containing butyl rubber, a tackifying resin, and ametal oxide serving as a vulcanizing agent. In particular, it wasconfirmed that anti-vibration rubbers molded from a rubber compositionin which a tackifying resin has a melting point of 100° C. or higher andthe content of the tackifying resin is 35 to 60 parts by mass, bothinclusive, per 100 parts by mass of a polymer component, have a verystrong ability to reduce vibration.

Example 2

Table 4 shows the contents of each component and the evaluation resultsof Samples 2, 11, and 12. Sample 2 in Table 4 is the same as Sample 2 inTable 1. Components of Samples 11 and 12 are specifically shown in Table2.

(Samples 11 and 12)

A polymer component, a tackifying resin, a filler, a vulcanizing agent,a vulcanization accelerator, and a processing aid were kneaded with akneading machine as shown in Tables 2 and 4 to produce a rubbercomposition of Sample 11. In addition, a polymer component, a tackifyingresin, a filler, a vulcanizing agent, and a vulcanization acceleratorwere kneaded with a kneading machine as shown in Tables 2 and 4 toproduce a rubber composition of Sample 12. Each of the rubbercompositions of Samples 11 and 12 was then vulcanized by heating at 160°C. for 30 minutes to produce anti-vibration rubbers of Samples 11 and12. A sulfur-based vulcanizing agent was used as a vulcanizing agent ofSample 11, and a resin vulcanizing agent was used as a vulcanizing agentof Sample 12. In Samples 11 and 12, zinc oxide was used as avulcanization accelerator.

(Evaluation Method)

As in Example 1, anti-vibration properties, processability, andcompression set were measured for Samples 11 and 12. The results areshown in Table 4. Regarding processability in Table 4, “Z” indicatesthere was adhesion of unvulcanized rubber and thus indicates poorprocessability.

TABLE 4 Sample 2 Sample 11 Sample 12 Polymer A 100 100 100 Component B CD Tackifying A Resin B 60 60 60 C D E F G Filler A 60 60 60 B C SoftenerA B Processing Aid A 1 1 B Vulcanizing A 5 Agent B C 2.5 D 5Vulcanization A 5 5 Accelerator B 1 Vulcanization C Accelerator Aid DPeak tan δTemperature (° C.) 35 34 37 tan δ (25° C./10 Hz) 1.2 1.18 1.25Anti-Vibration Properties Y Y Y Processability X X Z Compression Set (%)17 40 9

(Evaluation Results)

In temperature variance measurement of dynamic viscoelasticity at afrequency of 30 Hz, each of the anti-vibration rubbers of Samples 11 and12 had a maximum loss factor at a temperature of −10° C. to 40° C., bothinclusive, and had a loss factor of 0.4 or more in the entiretemperature range of −10° C. to 40° C., both inclusive, at the frequencyof 30 Hz.

However, as shown in Table 4, Sample 2 containing a metal oxide as avulcanizing agent exhibited lower compression set than Sample 11containing a sulfur-based vulcanizing agent as a vulcanizing agent.Sample 2 exhibited satisfactory compression set at high temperatures,which indicates that Sample 2 has excellent long-term reliability.

Sample 2 containing a metal oxide as a vulcanizing agent and containingstearic acid as a processing aid exhibited higher processability thanSample 12 containing a resin vulcanizing agent as a vulcanizing agentand containing no processing aid.

Referring to Table 1, Sample 1 and 3 to 6 also contain a metal oxide asa vulcanizing agent and contain stearic acid as a processing aid.Accordingly, it was found that, like Sample 2 shown in Table 4, Samples1 and 3 to 4 also exhibited satisfactory compression set and highprocessability.

It was found from Example 2 that the use of a metal oxide as avulcanizing agent can improve compression set in addition to providinghigh anti-vibration properties and that addition of a processing aid canfurther improve processability.

The embodiment and examples disclosed herein are by way of example inall respects and should not be interpreted as restrictive. The scope ofthe present invention is defined by the claims rather than by the aboveembodiment and examples, and the invention is intended to cover allchanges and modifications within the spirit and scope of the inventionas defined by the claims.

REFERENCE SIGNS LIST

-   -   1, 2 Drum-Type Washing Machine    -   3 Base    -   4 Outer Cabinet    -   6 Wash Tub    -   8 Spin Tub    -   11 Spring Body    -   12 Anti-Vibration Damper    -   31 Leg Rubber

The invention claimed is:
 1. A washing machine including ananti-vibration leg rubber, wherein: in a temperature variancemeasurement of dynamic viscoelasticity at a frequency of 30 Hz, saidanti-vibration rubber has a maximum loss factor at a temperature of −10°C. to 40° C., both inclusive, said anti-vibration rubber has a lossfactor of 0.4 or more in an entire temperature range of −10° C. to 40°C., both inclusive, at the frequency of 30 Hz, a compression permanentset of the anti-vibration rubber is 30% or less, said anti-vibration legrubber is attached to corners of a base of the washing machine, and saidanti-vibration rubber comprises a polymer component consistingessentially of butyl rubber.
 2. The washing machine according to claim1, wherein: said anti-vibration rubber comprises said polymer componentand a tackifying resin, and said anti-vibration rubber comprises 10 to60 parts by mass of said tackifying resin, both inclusive, per 100 partsby mass of said polymer component.
 3. The washing machine according toclaim 2, wherein said butyl rubber comprises a halogenated butyl rubber.4. The washing machine according to claim 1, wherein said anti-vibrationrubber further comprises a metal oxide as a vulcanizing agent.
 5. Thewashing machine according to claim 1, wherein said anti-vibration rubbercomprises a vulcanized rubber.
 6. The washing machine according to claim1, wherein said anti-vibration rubber further comprises a processingaid.